The present invention relates to a seatbelt apparatus equipped in a seat of an automobile or other transportation vehicles and a buckle of the seatbelt apparatus and, in particular, relates to a shock-proof device provided in the buckle for preventing a release button from releasing the buckle by inertia from a tongue inserted into and retained to the buckle using an inertia lever.
A seat of an automobile and various kinds of transportation vehicles has been equipped with a seatbelt for protecting an occupant from collision. In such a seatbelt, there is usually provided a buckle to simply put on or off the seatbelt. The buckle has a latch member having a claw for engaging a tongue urged by a spring in an engaging direction. In such a buckle, the tongue attached to the seatbelt is inserted into the buckle so that the latch member of the buckle engages the tongue, and then the latch member is held to the tongue with a release-preventing pin in an engaged state so as to fit the seatbelt to an occupant. A release button for releasing the engagement between the tongue and the buckle is pressed in a releasing direction so as to move the release-preventing pin to a non-retention position, thereby releasing the tongue from the buckle.
In order to securely engage the tongue with the buckle when a vehicle receives a large impact during a vehicle collision, various buckles having a shock-proof device have been proposed in which an inertia lever is rotatably provided in a body base for preventing the release button from moving in the releasing direction (see Deutsche Offenlegungsschrift No. 9202526.9 (DE9202526.9U1)).
In the buckle disclosed in Deutsche Offenlegungsschrift No. 9202526.9 (DE9202526.9U1), an inertial force of the release button itself is applied to the inertia lever on a surface perpendicular to the moving direction of the release button in any one of release and non-release directions of the release button.
In the shock-proof device disclosed Deutsche Offenlegungsschrift No. 9202526.9 (DE9202526.9U1), when the inertial force is applied in the release direction, the inertia lever prevents the release button from moving. However, it is necessary to increase moment of the inertial force of the inertia lever to be greater than that of the inertial force of the release button in order to securely prevent the movement in the non-release direction.
When the moments are set in such a manner, in the shock-proof device, when the inertial force is applied to the release button in the non-release direction, the release button attempts to move in the non-release. Since the inertia lever has an engagement part with a circular cross-section for engaging two vertical planes of the release button, the moment of the inertial force of the inertia lever becomes larger than that of the inertial force of the release button, so that the inertia lever may move the release button in the release direction.
Accordingly, it is necessary to set the moment of the inertial force of the inertia lever identical to that of the inertial force of the release button, so that the inertia lever does not move the release button in the release and non-release directions. In the shock-proof device, it is possible to set the moments identical. In this case, however, it is difficult to securely prevent the release button from moving in the release direction by the inertia lever when the inertial force is applied to the release button in the release and non-release directions.
As described above, in the shock-proof device disclosed in Deutsche Offenlegungsschrift No. 9202526.9 (DE9202526.9U1), it is difficult to prevent the disengagement between the tongue and the buckle depending on a direction of the inertial force.
In view of problems described above, the present invention has been made, and an object of the present invention is to provide a shock-proof device disposed in a buckle capable of securely preventing the disengagement between a tongue and a buckle regardless of a direction of the inertial force, a buckle having the shock-proof device, and a seatbelt apparatus having the buckle.
Further objects and advantages of the invention will be apparent from the following description of the invention.